Scintillator crystals, method for making same, use thereof

ABSTRACT

The invention concerns an inorganic scintillator material of general composition M1−xCexCl3, wherein: M is selected among lanthanides or lanthanide mixtures, preferably among the elements or mixtures of elements of the group consisting of Y, La, Gd, Lu, in particular among the elements or mixtures of elements of the group consisting of La, Gd and Lu; and x is the molar rate of substitution of M with cerium, x being not less than 1 mol % and strictly less than 100 mol %. The invention also concerns a method for growing said monocrystalline scintillator material, and the use of said scintillator material as component of a scintillating detector in particular for industrial and medical purposes and in the oil industry.

The present invention relates to scintillator crystals, to amanufacturing method allowing them to be obtained and to the use of saidcrystals, especially in gamma-ray and/or X-ray detectors.

Scintillator crystals are widely used in detectors for gamma-rays,X-rays, cosmic rays and particles whose energy is of the order of 1 keVand also greater than this value.

A scintillator crystal is a crystal which is transparent in thescintillation wavelength range, which responds to incident radiation byemitting a light pulse.

From such crystals, generally single crystals, it is possible tomanufacture detectors in which the light emitted by the crystal that thedetector comprises is coupled to a light-detection means and produces anelectrical signal proportional to the number of light pulses receivedand to their intensity. Such detectors are used especially in industryfor thickness or weight measurements and in the fields of nuclearmedicine, physics, chemistry and oil exploration.

A family of known scintillator crystals widely used is of thethallium-doped sodium iodide Tl:NaI type. This scintillating material,discovered in 1948 by Robert Hofstadter and which forms the basis ofmodern scintillators, still remains the predominant material in thisfield in spite of almost 50 years of research on other materials.However, these crystals have a scintillation decay which is not veryfast.

A material which is also used is CsI which, depending on theapplications, may be used pure, or doped either with thallium (Tl) orwith sodium (Na).

One family of scintillator crystals which has undergone considerabledevelopment is of the bismuth germanate (BGO) type. The crystals of theBGO family have high decay time constants, which limit the use of thesecrystals to low count rates.

A more recent family of scintillator crystals was developed in the 1990sand is of the cerium-activated lutetium oxyorthosilicate Ce:LSO type.However these crystals are very heterogeneous and have very high meltingpoints (about 2200° C.).

The development of new scintillating materials for improved performanceis the subject of many studies. One of the parameters that it is desiredto improve is the energy resolution.

This is because in the majority of nuclear detector applications, goodenergy resolution is desired. The energy resolution of a nuclearradiation detector actually determines its ability to separate radiationenergies which are very close. It is usually determined for a givendetector at a given energy, such as the width at mid-height of the peakin question on an energy spectrum obtained from this detector, inrelation to the energy at the centroid of the peak (see in particular:G. F. Knoll, “Radiation Detection and Measurement”, John Wiley and Sons,Inc., 2nd edition, p. 114). In the rest of the text, and for allmeasurements carried out, the resolution is determined at 662 keV, theenergy of the main gamma emission of ¹³⁷Cs.

The smaller the value of the energy resolution, the better the qualityof the detector. It is considered that energy resolutions of about 7%enable good results to be obtained. Nevertheless, lower values ofresolution are of great benefit.

For example, in the case of a detector used to analyze variousradioactive isotopes, improved energy resolution enables improveddiscrimination of these isotopes.

An increase in the energy resolution is particularly advantageous for amedical imaging device, for example of the Anger gamma-camera orpositron emission tomography (PET) type, since it enables the contrastand the quality of the images to be considerably improved, thus allowingmore accurate and earlier detection of tumors.

Another very important parameter is the scintillation decay timeconstant; this parameter is usually measured by the “Start Stop” or“Multi-hit” method, (described by W. W. Moses (Nucl. Instr and Meth.A336 (1993)253).

The smallest possible decay time constant is desired, so as to be ableto increase the operating frequency of the detectors. In the field ofnuclear medical imaging, this makes it possible, for example, toconsiderably reduce the length of examinations. A decay time constantwhich is not very high also enables the temporal resolution of devicesdetecting events with temporal coincidence to be improved. This is thecase for positron emission tomographs (PET), where the reduction in thescintillator decay time constant enables the images to be significantlyimproved by rejecting noncoincident events with more accuracy.

In general, the spectrum of scintillation decay as a function of timemay be broken down into a sum of exponentials, each characterized by adecay time constant.

The quality of a scintillator is essentially determined by theproperties of the contribution from the fastest emission component.

The standard scintillating materials do not allow both good energyresolutions and fast decay time constants to be obtained.

This is because materials such as Tl:NaI have good energy resolutionunder gamma excitation, of about 7%, but a high decay time constant ofabout 230 ns. Similarly, Tl:CsI and Na:CsI have high decay timeconstants, especially greater than 500 ns.

Decay time constants which are not very high can be obtained withCe:LSO, especially of about 40 ns, but the energy resolution under gammaexcitation at 662 keV of this material is generally greater than 10%.

Recently, scintillating materials have been disclosed by O. Guillot-Noëlet al. (“Optical and scintillation properties of cerium doped LaCl₃,LuBr₃ and LuCl₃” in Journal of Luminescence 85 (1999) 21-35). Thisarticle describes the scintillation properties of cerium-doped compoundssuch as LaCl₃ doped with 0.57 mol % Ce; LuBr₃ doped with 0.021 mol %,0.46 mol % and 0.76 mol % Ce; LuCl₃ doped with 0.45 mol % Ce. Thesescintillating materials have quite useful energy resolutions, of theorder of 7%, and decay time constants of the fast scintillationcomponent which are fairly low, especially between 25 and 50 ns.However, the intensity of the fast component of these materials is low,especially of the order of 1000 to 2000 photons per MeV, which meansthat they cannot be used as a component of a high-performance detector.

This object of the present application relates to a material capable ofhaving simultaneously a good energy resolution, especially at least asgood as that of Tl:NaI, a low decay time constant, especially at leastequivalent to that of Ce:LSO, and where the intensity of the fastscintillation component is suitable for producing high-performancedetectors, in particular is greater than 4000 ph/MeV (photons per MeV),or even greater than 8000 ph/MeV (photons per MeV).

According to the invention, this aim is achieved by an inorganicscintillating material of general composition M_(1−x)Ce_(x)Cl₃, where Mis chosen from the lanthanides or mixtures of lanthanides, preferablyfrom the elements or the mixtures of elements of the group: Y, La, Gd,Lu, especially from the elements or the mixtures of elements of thegroup: La, Gd, Lu, and where x is the molar level of substitution of Mby cerium, subsequently called “cerium content”, where x is greater thanor equal to 1 mol % and strictly less than 100 mol %.

The term “lanthanide” refers to the transition elements of atomicnumbers 57 to 71, and to yttrium (Y), as is standard in the technicalfield of the invention.

An inorganic scintillating material according to the inventionsubstantially consists of M_(1−x)Ce_(x)Cl₃ and may also compriseimpurities usual in the technical field of the invention. In general,the usual impurities are impurities coming from the raw materials whosecontent is in particular less than 0.1%, or even less than 0.01%, and/orthe unwanted phases whose volume percentage is especially less than 1%.

In fact, the inventors have known how to show that the M_(1−x)Ce_(x)Cl₃compounds defined above, where the cerium content is greater than orequal to 1 mol %, have remarkable properties. The scintillation emissionof the materials according to the invention has an intense fastcomponent (of at least 4000 ph/MeV) and a low decay time constant, ofthe order of 25 ns. At the same time, these materials have excellentenergy resolution at 662 keV, in particular less than 5%, and even than4%.

These properties are even more remarkable since they are unexpected andhighlight a considerable discontinuity of properties starting from 1 mol% of cerium. This choice of composition is even more surprising sincethe cerium-doped scintillators having good performance, such as LSO,contain less than 1% cerium, and preferably about 0.2% (see for exampleM.Kapusta et al., “Comparison of the scintillation properties of LSO:Cemanufactured by different laboratories and of LGSO:Ce”, IEEE transactionon nuclear science, Vol. 47, No. 4, August 2000).

A preferred material according to the invention has the formulaLa_(1−x)Ce_(x)Cl₃.

According to one embodiment, the scintillating material according to theinvention has an energy resolution of less than 5%.

According to another embodiment, the scintillating material according tothe invention has a fast decay time constant of less than 40 ns, or evenof less than 30 ns.

According to a preferred embodiment, the scintillating materialaccording to the invention has both an energy resolution less than 5%and a fast decay time constant of less than 40 ns, or even less than 30ns.

In a preferred manner, the cerium content x is between 1 mol % and 90mol %, and even in particular greater than or equal to 2 mol %, or evengreater than or equal to 4 mol % and/or preferably less than or equal to50 mol %, or even less than or equal to 30 mol %.

According to one embodiment, the scintillating material according to theinvention is a single crystal making it possible to obtain components ofhigh transparency, the dimensions of which are enough to efficientlystop and detect the radiation to be detected, including at high energy.The volume of these single crystals is in particular of the order of 10mm³, or even greater than 1 cm³ and even greater than 10 cm³.

According to another embodiment, the scintillating material according tothe invention is a powder or polycrystal, for example in the form ofpowders mixed with a binder or else in the form of a sol-gel.

The invention also relates to a method for obtaining the scintillatingmaterial M_(1−x)Ce_(x)Cl₃ defined above, in the form of a single crystalby the Bridgman growth method, for example in evacuated sealed quartzampoules, in particular from a mixture of commercial MCl₃ and CeCl₃powders.

The invention also relates to the use of the scintillating materialabove as a component of a detector for detecting radiation in particularby gamma rays and/or X-rays.

Such a detector especially comprises a photodetector optically coupledto the scintillator in order to produce an electrical signal in responseto the emission of a light pulse produced by the scintillator.

The photodetector of the detector may in particular be aphotomultiplier, or else a photodiode, or else a CCD sensor.

The preferred use of this type of detector relates to the measurement ofgamma or X-ray radiation; such a system is also capable of detectingalpha and beta radiation and electrons. The invention also relates tothe use of the above detector in nuclear medicine apparatuses,especially gamma cameras of the Anger type and positron emissiontomography scanners (see for example C. W. E. Van Eijk, “InorganicScintillator for Medical Imaging”, International Seminar New types ofDetectors, May 15-19, 1995—Archamp, France. Published in “PhysicaMedica”, Vol. XII, supplement 1, June 96).

According to another variant, the invention relates to the use of theabove detector in detection apparatuses for oil drilling, (see forexample “Applications of scintillation counting and analysis”, in“Photomultiplier tube, principle and application”, chapter 7, Philips).

Other details and characteristics will emerge from the description belowof preferred nonlimiting embodiments and of data obtained on samplesconstituting single crystals according to the invention.

Table 1 shows the characteristic scintillation results for examplesaccording to the invention (examples 1 to 5) and for comparativeexamples (examples A to D). x is the cerium content, expressed in mol %,substituted into the atom M.

The measurements are carried out under γ-ray excitation at 662 keV. Themeasurement conditions are specified in the publication by O.Guillot-Noël, cited above.

The emission intensity is expressed in photons per MeV.

The emission intensity is recorded as a function of the integration timeup to 0.5; 3 and 10 microseconds.

The fast scintillation component is characterized by its decay timeconstant, τ, in nanoseconds, and by its scintillation intensity (inphotons/MeV), which represents the contribution of this component to thetotal number of photons emitted by the scintillator.

The samples used in the measurements of examples A to D and 1 to 3 and 5are small single crystals of about 10 mm³, and the sample of example 4is a relatively large single crystal with a diameter of 8 mm and aheight of 5 mm. Good reproducibility of the results obtained was noticedbetween the small (ex3) and large (ex4) samples.

From table 1, it is noticed that the compounds of the M_(1−x)Ce_(x)Cl₃type comprising less than 1 mol % cerium (examples A, D) have an energyresolution greater than 7% and low intensities of the fast scintillationcomponent (of the order of 1500 ph/MeV) . The undoped LaCl₃ has a decaytime constant of the first component of about 3500 ns (exC), and istherefore extremely slow.

In the case of a fluorinated compound doped at more than 1 mol % cerium(example B), the scintillation decay is very fast but the overallscintillation efficiency is very low.

The examples according to the invention, ex1 to ex5, all have veryadvantageous decay time constants of the fast fluorescence component,between 20 and 30 ns, and the scintillation intensity of this fastcomponent is remarkable and is greater that 4000 ph/MeV. It reachesabout 20000 ph/MeV for a material comprising 10 mol % cerium.

In addition, the resolution, R, of these examples according to theinvention is excellent and has an unexpected nature.

This is because, from the statistical point of view, it is accepted thatthe energy resolution varies in proportion to the inverse of the squareroot of the total number of photons emitted (see in particular: G. F.Knoll, “Radiation detection and measurement”, John Wiley and Sons, Inc,2^(nd) edition, p 116). This total number of photons corresponds to theemission intensity at saturation, which is measured by the emissionintensity value at 10 μs.

By considering the total number of photons emitted by LaCl₃ comprisingmore than 1 mol % cerium compared with LaCl3 doped at 0.57 mol %, asmall improvement of the resolution of at best 5% is expected, thelatter therefore going from 7.3% to about 6.9%.

In a particularly surprising manner, the inventors noticed aconsiderable improvement in the energy resolution for a cerium contentgreater than 1 mol % in the M_(1−x)Ce_(x)Cl₃ materials. This improvementis by a factor of about 2 for LaCl₃ comprising 2 mol %, 4 mol %, 10 mol%, 30 mol % cerium (examples 1 to 5).

Scintillating materials having such a performance are particularlysuitable for increasing the performance of detectors, both in terms ofenergy resolution, temporal resolution and count rate.

TABLE 1 Emission Intensity Fast Component x: (photons/MeV) Resolution:Intensity Example Matrix mol % Ce³⁺ 0.5 μs 3 μs 10 μs (R %) τ(ns)(ph/MeV) A LuCl₃ 0.45 1300 3500 5700 18 50 1425 B LaF₃ 10 2200 22002200 >20 3 220 C LaCl₃ 0 34000 4.9 3480 34000 D LaCl₃ 0.57 19000 3700044000 7.3 24 1300 ex1 LaCl₃ 2 44000 49000 3.7 27 4900 ex2 LaCl₃ 4 3600047000 49000 3.4 25 8800 ex3 LaCl₃ 10 45000 49000 49000 3.7 26 20100 ex4LaCl₃ 10 45000 49000 49000 3.3 26 18500 ex5 LaCl₃ 30 42000 43000 430003.3 24 29700

1. A method of detecting radiation, comprising the steps of: receivingsaid radiation with an inorganic scintillating material comprisingM_(1−x)Ce_(x)Cl₃ where M is chosen from the elements or the mixtures ofelements of the group of the lanthanides and Y and where x is the molarlevel of substitution of M by cerium, where x is greater than or equalto 1 mol % and less than 100 mol %; emitting light with said inorganicscintillating material in response to said step of receiving saidradiation, wherein said emitted light has a fast scintillation componenthaving an emission intensity of at least 4000 photons per MeV; anddetecting said light with a photodetector.
 2. The method as claimed inclaim 1, wherein M is chosen from the elements or the mixtures ofelements of the group: Y, La, Gd, Lu.
 3. The method as claimed in claim1, wherein M is lanthanum (La).
 4. The method as claimed in claim 1,wherein x is greater than or equal to 2 mol %.
 5. The method as claimedin claim 1, wherein x is greater than or equal to 4 mol %.
 6. The methodas claimed in claim 1, wherein x is less than or equal to 90 mol %. 7.The method as claimed in claim 1, wherein the energy resolution of theinorganic scintillating material is less than 5% for a measurement withgamma photons at 662 keV.
 8. The method as claimed in claim 1, wherein xis greater than or equal to 2 mol % and wherein M is lanthanum (La). 9.The method as claimed in claim 1, wherein x is greater than or equal to4 mol % and wherein M is lanthanum (La).
 10. The method as claimed inclaim 1, wherein the fast scintillation component has an emissionintensity of at least 8000 photons per MeV.
 11. The method as claimed inclaim 3, wherein the fast scintillation component has an emissionintensity of at least 8000 photons per MeV.
 12. The method as claimed inclaim 1, wherein the fast scintillation component has a decay timeconstant of at most 30 ns.
 13. The method of claim 1, wherein theinorganic scintillating material has an energy resolution of at most 4%at 662 keV.
 14. The method of claim 1, wherein the fast scintillationcomponent has an emission intensity of at least 8000 photons per MeV anda decay time constant of at most 30 ns.
 15. The method as claimed inclaim 14, wherein the inorganic scintillating material has an energyresolution of at most 4% at 662 keV.
 16. The method of claim 1, whereinthe inorganic scintillating material consists of M_(1−x)Ce_(x)Cl₃.
 17. Amethod of detecting radiation, comprising the steps of: receiving saidradiation with an inorganic scintillating material comprising M, Ce, andCl wherein M is selected from the group consisting of the lanthanides,Y, and combinations thereof, and M is partially substituted by Ce, amolar level of substitution of M by Ce being greater than or equal to 1mol % and less than 100 mol %; emitting light with said inorganicscintillating material in response to said step of receiving saidradiation; and detecting said light with a photodetector.
 18. The methodas claimed in claim 17, wherein M is chosen from the elements or themixtures of elements of the group: Y, La, Gd, Lu.
 19. The method asclaimed in claim 17, wherein M is lanthanum (La).
 20. The method asclaimed in claim 17, wherein the inorganic scintillating material is inthe form of a single crystal.
 21. The method as claimed in claim 20,wherein the single crystal has a volume greater than 10 mm³.
 22. Themethod as claimed in claim 20, wherein the single crystal has a volumegreater than 1 cm³.
 23. The method as claimed in claim 20, wherein thesingle crystal has a volume greater than 10 cm³.
 24. The method asclaimed in claim 17, wherein the molar level of substitution of M by Ceis greater than or equal to 2 mol %.
 25. The method as claimed in claim17, wherein the molar level of substitution of M by Ce is greater thanor equal to 4 mol %.
 26. The method as claimed in claim 17, wherein themolar level of substitution of M by Ce is less than or equal to 90 mol%.
 27. The method as claimed in claim 17, wherein the inorganicscintillating material comprises M_(1−x)Ce_(x)Cl₃ where x is the molarlevel of substitution of M by Ce.
 28. The method as claimed in claim 17,wherein the inorganic scintillating material consists ofM_(1−x)Ce_(x)Cl₃ where x is the molar level of substitution of M by Ce.29. The method as claimed in claim 17, wherein the energy resolution ofthe inorganic scintillating material is less than 5% for a measurementwith gamma photons at 662 keV.
 30. The method as claimed in claim 17,wherein the scintillating material is a powder or a polycrystal.
 31. Aradiation detector comprising: an inorganic scintillating materialcomprising M_(1−x)Ce_(x)Cl₃ where M is chosen from the elements or themixtures of elements of the group of the lanthanides and Y and where xis the molar level of substitution of M by cerium, where x is greaterthan or equal to 1 mol % and less than 100 mol %; and a photodetectorbeing coupled to said inorganic scintillating material, wherein whensaid inorganic scintillating material is exposed to radiation saidinorganic scintillating material is capable of emitting light having afast scintillation component with an emission intensity of at least 4000photons per MeV.
 32. The radiation detector as claimed in claim 31,wherein M is chosen from the elements or the mixtures of elements of thegroup of Y, La, Gd, Lu.
 33. The radiation detector as claimed in claim31, wherein M is lanthanum (La).
 34. The radiation detector as claimedin claim 31, wherein the inorganic scintillating material is in the formof a single crystal.
 35. The radiation detector as claimed in claim 34,wherein the single crystal has a volume greater than 10 mm³.
 36. Theradiation detector as claimed in claim 34, wherein the single crystalhas a volume greater than 1 cm³.
 37. The radiation detector as claimedin claim 34, wherein the single crystal has a volume greater than 10cm³.
 38. The radiation detector as claimed in claim 31, wherein x isless than or equal to 90 mol %.
 39. The radiation detector as claimed inclaim 31, wherein x is greater than or equal to 2 mol %.
 40. Theradiation detector as claimed in claim 31, wherein x is greater than orequal to 4 mol %.
 41. The radiation detector as claimed in claim 31,wherein the energy resolution of the inorganic scintillating material isless than 5% for a measurement with gamma photons at 662 keV.
 42. Theradiation detector as claimed in claim 31, wherein the scintillatingmaterial is a powder or a polycrystal.
 43. The radiation detector asclaimed in claim 31, wherein x is less than or equal to 90 mol % and isgreater than or equal to 4 mol % and wherein M is lanthanum (La). 44.The radiation detector as claimed in claim 31, wherein said fastscintillation component has a decay time constant of at most 30 ns. 45.The radiation detector of claim 31, wherein the inorganic scintillatingmaterial has an energy resolution of at most 4% at 662 keV.
 46. Theradiation detector of claim 31, wherein said fast scintillationcomponent has an emission intensity of at least 8000 photons per MeV.47. The radiation detector of claim 31, wherein said fast scintillationcomponent has an emission intensity of at least 8000 photons per MeV anda decay time constant of at most 30 ns.
 48. The radiation detector ofclaim 31, wherein said radiation includes gamma rays.
 49. The radiationdetector of claim 31, wherein said radiation includes X-rays.
 50. Ascintillation detector comprising: an inorganic scintillating materialcomprising M, Ce, and Cl wherein M is selected from the group consistingof the lanthanides, Y, and combinations thereof, and M is partiallysubstituted by Ce, a molar level of substitution of M by Ce beinggreater than or equal to 1 mol % and less than 100 mol %; and aphotodetector coupled to said inorganic scintillating material.
 51. Thescintillation detector as claimed in claim 50, where M is chosen fromthe elements or the mixtures of elements of the group: Y, La, Gd, Lu.52. The scintillation detector as claimed in claim 50, wherein M islanthanum (La).
 53. The scintillation detector as claimed in claim 50,wherein the inorganic scintillating material is in the form of a singlecrystal.
 54. The scintillation detector as claimed in claim 53, whereinthe single crystal has a volume greater than 10 mm³.
 55. Thescintillation detector as claimed in claim 53, wherein the singlecrystal has a volume greater than 1 cm³.
 56. The scintillation detectoras claimed in claim 53, wherein the single crystal has a volume greaterthan 10 cm³.
 57. The scintillation detector as claimed in claim 50,wherein the molar level of substitution of M by Ce is greater than orequal to 2 mol %.
 58. The scintillation detector as claimed in claim 50,wherein the molar level of substitution of M by Ce is greater than orequal to 4 mol %.
 59. The scintillation detector as claimed in claim 50,wherein the molar level of substitution of M by Ce is less than or equalto 90 mol %.
 60. The scintillation detector as claimed in claim 50,wherein the inorganic scintillation material comprises M_(1−x)Ce_(x)Cl₃where x is the molar level of substitution of M by Ce.
 61. Thescintillation detector as claimed in claim SO, wherein the inorganicscintillating material consists of M_(1−x)Ce_(x)Cl₃ where x is the molarlevel of substitution of M by Ce.
 62. The scintillation detector asclaimed in claim 50, wherein the energy resolution of the inorganicscintillating material is less than 5% for a measurement with gammaphotons at 662 keV.
 63. The scintillation detector as claimed in claim50, wherein the scintillating material is a powder or a polycrystal. 64.A method of generating a fast scintillation component with an emissionintensity greater than 4000 ph/Mev, comprising: exposing to radiation aninorganic scintillating material comprising M, Ce and Cl wherein M isselected from the elements or the mixtures of elements of the group ofthe lanthanides and Y, and M is partially substituted by Ce, a molarlevel of substitution of M by Ce being greater than or equal to 1 mol %and less than 100 mol %, emitting light from said inorganicscintillating material in response to said exposing, wherein saidemitted light has a fast scintillation component having has an emissionintensity greater than 4000 ph/Mev.
 65. The method as claimed in claim64, wherein M is chosen from the elements or the mixtures of elements ofthe group: Y, La, Gd, Lu.
 66. The method as claimed in claim 64, whereinM is lanthanum (La).
 67. The method as claimed in claim 64, wherein theinorganic scintillating material is in the form of a single crystal. 68.The method as claimed in claim 67, wherein the single crystal has avolume greater than 10 mm³.
 69. The method as claimed in claim 67,wherein the single crystal has a volume greater than 1 cm³.
 70. Themethod as claimed in claim 67, wherein the single crystal has a volumegreater than 10 cm³.
 71. The method as claimed in claim 64, wherein themolar level of substitution of M by Ce is greater than or equal to 2 mol%.
 72. The method as claimed in claim 64, wherein the molar level ofsubstitution of M by Ce is greater than or equal to 4 mol %.
 73. Themethod as claimed in claim 64, wherein the molar level of substitutionof M by Ce is less than or equal to 90 mol %.
 74. The method as claimedin claim 64, wherein the inorganic scintillating material comprisesM_(1−x)Ce_(x)Cl₃ where x is the molar level of substitution of M by Ce.75. The method as claimed in claim 64, wherein the inorganicscintillating material consists of M_(1−x)Ce_(x)Cl₃ where x is the molarlevel of substitution of M by Ce.
 76. The method as claimed in claim 64,wherein the energy resolution of the inorganic scintillating material isless than 5% for a measurement with gamma photons at 662 keV.
 77. Themethod as claimed in claim 64, wherein the scintillating material is apowder or a polycrystal.
 78. A method of increasing the emissionintensity of a fast scintillation component of an inorganicscintillating material when exposed to radiation to at least 4000ph/Mev, said method comprising combining M, Ce and Cl to form aninorganic scintillating material, wherein M is selected from theelements or the mixtures of elements of the group of the lanthanides andY, and wherein the molar level of Ce present in the inorganicscintillating material is greater than or equal to 1 mol % and less than100 mol %.
 79. A scintillation detector configured to generate a fastscintillation component with an emission intensity greater than 4000ph/Mev, said scintillation detector comprising: means for exposing toradiation an inorganic scintillating material comprising M, Ce and Clwherein M is selected from the elements or the mixtures of elements ofthe group of the lanthanides and Y, and M is partially substituted byCe, a molar level of substitution of M by Ce being greater than or equalto 1 mol % and less than 100 mol %, and means for emitting light fromsaid inorganic scintillating material in response to said exposing,wherein said emitted light has a fast scintillation component having hasan emission intensity greater than 4000 ph/Mev.